This invention relates to a magnetic disc having crests and valleys formed in its magnetic recording area. More particularly, it relates to a magnetic disc in which contact start stop (CSS) with respect to a slider carrying a magnetic head for writing/readout on or from a magnetic disc may be performed in stability.
A magnetic recording medium for recording/reproducing the digital information by a magnetic head, such as a magnetic disc, has servo marks, that is recorded position signals, formed thereon for tracking the magnetic head. The "tracking" herein means causing the magnetic head to correctly follow a recording track bearing a desired address.
These servo marks are recorded by a servo writer simultaneously with data recording. With progress in high density recording and concomitant reduction in the recording track width, high servo mark position density has become necessary, such that it has become necessary to maintain high position accuracy between the servo writer and the associated mechanical components of the magnetic recording apparatus. Since this necessitates a high technical level, the recording/reproducing apparatus becomes costly.
Thus a variety of methods have been proposed for raising position signal accuracy by pre-forming servo marks on a magnetic disc. Among these are a method of forming servo marks by etching a magnetic layer or non-magnetizing a portion of the magnetic layer, and a method of forming servo marks by forming crests and valleys in a disc substrate.
In forming servo marks by crests and valleys, since the recording tracks and guard bands separating the recording tracks from one another may be formed simultaneously as crests and valleys, respectively, a so-called discrete type magnetic disc may be formed easily. With the magnetic disc, having the servo marks and the recording tracks thus formed by crests and valleys, recording/readout may be performed with a high track-pitch tracking operation and at a high signal-to-noise ratio.
Referring to FIG. 1, an illustrative magnetic disc, as loaded on a floating magnetic head recording/reproducing apparatus, is explained in detail.
The magnetic disc 101 has a magnetic recording area 102 for writing/reading the information by a magnetic head, a clamping area 103 on the inner rim of the disc and a landing area 104 on the outer rim of the disc.
The magnetic recording area 102 has a data area 105 made up of convex-shaped recording tracks and recessed guard bands, and a servo area 106, in the form of crests and valleys, for radially dividing the data area 105.
The magnetic disc 101 is loaded on the floating magnetic head type recording/reproducing apparatus, by the clamping area 103 being secured by the damper 114, and is rotated by a spindle motor, not shown.
On top of the magnetic disc 101 is supported a slider 111 carrying the magnetic head by an arm 112, which is rotated with a rotary shaft 113 as the center of rotation for shifting the slider 111 along the radius of the magnetic disc 101.
For floating the slider 111 above the magnetic disc 101, the slider is set in a CSS area inwardly of the magnetic recording area 102. The slider 111 is floated on starting rotation of the magnetic disc 101. When the slider 111 is floated, it is shifted by the arm 112 to a position overlying the magnetic recording area in order to follow the desired recording track in the data recording area 105 for writing/reading. After termination of the writing/reading, the rotation of the magnetic disc 101 is terminated for again landing the slider in the CSS area.
Although the CSS area is not an area of actually writing and/or reading the information, it is within an area within which the slider 111 is moved on driving the floating magnetic head type recording/reproducing apparatus. For this reason, it may be envisaged to provide a pattern of crests and valleys similar to that provided in the magnetic recording area 102. In such case, a pattern of crests and valleys similar to the pattern of the recording tracks and the guard bands is provided in the portion of the CSS area representing the radial continuation of the servo area 106, referred to herein as a CSS servo area. Similarly, a pattern of crests and valleys similar to that of the servo marks is provided in the portion of the CSS area representing the radial continuation of the servo area 106, referred to herein as a CSS servo area.
However, if contact-start-stop is actually performed in the CSS area having a pattern of crests and valleys similar to those in the magnetic recording area 102, powder debris is incurred by frictional contact between the slider 111 and the CSS area. This is presumably attributable to the fact that, since the relative proceeding direction of the slider 111 and the pattern of crests and valleys in the CSS servo area are substantially at right angles to each other, the crests in the CSS servo area scraped off the surface of the slider 111.
The powder debris thus produced give rise to injuries to the slider 111 and the magnetic disc 101.
On the other hand, the fact that the relative proceeding direction of the slider 111 and the pattern of crests and valleys of the CSS servo area are substantially at right angles to each other renders the float amount of the slider 111 liable to deteriorate the floating posture of the slider 111.